Japan has some of the busiest and largest rail hubs in the world, with multiple floors, overlapping rail lines and subterranean shopping arcades. The new platform uses smartphone motion sensors to track direction when a user walks around. The data is plotted against preloaded maps from Zenrin, which supplies mapping apps for all DoCoMo mobile phones.

Atmospheric pressure sensors, or barometers, in some smartphones can also be used to detect when users of the navigation service climb or descend stairs or use elevators, according to DoCoMo. When that happens, the appropriate map for the floor or outdoor environment is automatically called up.

"There's strong demand for a low-cost indoor navigation service," Takuya Ori, a spokesman for NTT DoCoMo, said via email, adding there are no comparable navigation apps that use sensors in smartphones.

DoCoMo plans to roll out the feature from April in Japan as an add-on to its Android map application. It will start with 320 indoor locations around the country, and the monthly user fee will likely be around ¥300 (£1.65).

The service will likely start with Android smartphones that have the appropriate sensors. DoCoMo also carries the iPhone 6, which includes a barometer that can determine relative elevation.